Technology is increasingly being used to track individuals as they visit retail shops and other locations. As one example, door counting devices can be used by a retail store to track the number of visitors to a particular store (e.g., entering through a particular door or set of doors) each day. As another example, in-store cameras can be used to monitor the movements of visitors (e.g., observing whether they turn right or left after entering the store). A variety of drawbacks to using such technologies exist. One drawback is cost: monitoring technology can be expensive to install, maintain, and/or run. A second drawback is that such technology is limited in the insight it can provide. For example, door counts do not distinguish between employees (who might enter and leave the building repeatedly during the course of the day) and shoppers. A third drawback is that such technology can be overly invasive. For example, shoppers may object to being constantly surveilled by cameras—particularly when the cameras are used for reasons other than providing security (e.g., assessing reactions to marketing displays).